Adjusting device for shoes of brakes of the drum type



y 1950 P. FARKAS 2,506,201

ADJUSTING DEVICE FOR SHOES 0F BRAKES OF THE DRUM TYPE Original Filed May27, I946 i E w,

I INVENTOR N P/erre Far/(as 4 TTORNE).

Patented May 2, 1950 ADJUSTING DEVICE FOR SHOES OF BRAKES OF THE DRUMTYPE Pierre Farkas, Paris, France Original application May 27, 1946,Serial No.

672,516. Divided and this application November 13, 1947, Serial No.785,751. In France November 18, 1942 Section 1, Public Law 690, August8, 1946 Patent expires November 18, 1962 4 Claims. (Cl. 188-795) This isa division of applicants copendin application Serial Number 672,516,filed May 27, 1946.

The present invention relates to an improved device for adjusting theposition of the expanding shoes of a brake of the drum type, in order tocompensate for wear, whether uniform or not, of the linings of two ormore sleeves.

A known form of brake of this kind comprises a pair of arcuate shoesmounted on a relatively fixed back-plate with one pair or adjacent endsof the shoes spring urged against some form of expander with which theycan be urged apart against the drum so as to produce a desired brakingeffect. It is also known to connect the other pair of adjacent endstogether in such a way that the separation between these ends may alsobe increased when desired, by hand, so as to compensate for wear of thelinings.

It is an object of the present invention to provide an improvedadjusting device which (a) serves to return the shoes to their offpositions after each normal application of the brakes, (1)) servesautomatically to correct for unequal wear of the linings of the shoes,and can be used to take up the shoes to compensate for equal wear of thelinings.

With these objects in view, and in accordance with the invention, thereis provided a wearcompensating device for brakes of the drum andexpanding shoes type, including a brake drum, a relatively fixedback-plate, a pair of arcuate shoes, brake-operated means for expandingone pair of adjacent ends, an adjusting member adjustably connected toboth shoes and to the back-plate.

Preferred embodiments of the invention will now be described withreference to the accompanying drawings, in which Figure 1 is a side Viewin elevation, partly in section, of a mechanical brake incorporating theinvention,

Figure 2 is a cross-sectional view taken on the line IIII of Figure 1,

Figure 3 is an enlarged cross-sectional view taken on the line IIIIII ofFigure 1,

Figure 4 is a plan view of a portion of the adjusting device shown inthe earlier figures, and

Figure 5 is a cross-sectional view similar to that of Fig. 3 but showinga modification of the invention.

The brake illustrated in Figures 1, 2 and 3 comprises a back plate 20rigidly secured to a vehicle, a brake drum 2| fixed to a road. wheel ofthe vehicle, and mounted on the back-plate 20 a pair of arcuatebrake-shoes 22 and 23, which 2 may be respectively split at it and tl ifdesired, a device 24 for taking up wear of the lining on the shoes andon which the shoes are pivoted, a wedge-shaped abutment 25 having radialfaces. against which one pair of adjacent ends of the shoes may bear,and a bracket 26 serving to hold and locate a sheathed brake-operatingcable 21 ending in a bifurcated hook 28 engaging shoeexpanding togglemechanism in the form of a double bell-crank lever 22 and a double link30.

The two parts of the parallel pair of links, which can be seen at 3B and36 in Figure 2, are kept in suitably spaced disposition by a washer 3|mounted on a peg 32 fixed on the back-plate 26, while the bifurcatedhook 23 is urged to its uppermost position by a helical spring 33compressed between a collar 32 on the hook and the bracket 25.

The double link is pivoted on the shoe 22 at 35 and the shorter arm'ofthe double bellcrank lever 29 is pivoted on the other shoe 23 at 36, thelever and link bein pivoted together at 31 to constitute'the knuckle ofthe toggle joint which is operated by movement of the longer arm of thebeli-crank lever by the hook 28 operated by the cable 21.

The top adjacent ends of the shoes 22 and 23 are urged against thesegmental abutment 25 by a pair of helical springs 38 and 39, and areurged into pivotal contact with the wear-compensating device 24 at theirlower ends by a sprin 42.

The compensating device 24, besides permitting the transmission ofmovement from one shoe to the other, can also be used to compensate forwear of the shoe-linings, whether equal or not, by separating the lowerends of the shoes.

The device comprises a two-piece dust-tight housing 43 (Figure 2) fixedon the back-plate 20, the two parts of which housing are securedtogether by stirrups 43 and M (Figure 1). The shoes 22 and 23 aremovably engaged in slots 45 and 46 respectively formed in yokes s1 and48 provided with oppositely threaded fingers 49 and 56 (Figure 4)engaging a single correspondingly threaded sleeve 5|. One longitudinalportion of this sleeve is cylindrical and the remainder, at 52, is ofpolygonal section on which is relatively slidable but angularly fast, abevel pinion 53 meshing with a second bevel pinion 54 secured on the endof a shaft 55 the outer end 56 of which is squared to take an adjustingkey or spanner.

The pinion 53 nests in a recessed seating in the housing 43, so that itis longitudinally immova- :ble, but the sleeve 5|, 52 can reciprocate,in the longitudinal direction, within this pinion.

Around the cylindrical sleeve portion is mounted a spiral spring 51housed in a recess 58, the innermost turn 51' of the spring being atight frictional grip on the sleeve 5'! so that normally when the sleevereciprocates within a certain predetermined range the spring is drawnalong with the sleeve, but if the sleeve moves outside this range thespring drags along the. sleeve to a new Position.

Th device 24 functions in the following way:

So long as the movement of the shoes is such that the innermost turn5110f the springdoes not exceed the distance between theundistortedposition of th spring (shown in Figure 3) and the inside wallof its housing 58, the spring remains in the same position on thesleeve- 51 and serves as a return spring to bring the sleeve 5| back toits normal position. This movement allows the self-wrapping action ofthe shoes to take place and for small inequalities of wear between theshoes.

If,,however, due to larger inequalities ofwear, thev sleeve 5! is movedexcessively to the right'or left, the turn 51 of the spring is firstbrought into contactwith an internal wall .of its housing and thereafterdrags on the sleeve 5| to take up a new mean position thereon.

Normal wear istaken up by turning the squared .end 56 of the shaft55'which serves to rotate pinion .53 and thus: separate the yokes 47 and48 carrying the lower ends of the shoes 22 and 23.

In Figure 5 there is illustrated a modification the wear compensatingdevice in which the spring 51. ofFigureS is replaced by a resilientwasher 59 the periphery-of which engages the extremity of the oblatespheroidal recess 60 in the housing and the inner wall of which engagesbetween flanges 6| formed on a split collar 62 which is a tight pressfit on the cylindrical portion of the sleeve 5 I The washer 55 takes theplace of the spring 51 of Figure 3, otherwise the-device functions in amanner similar to that-of -Figure 3.

The resilient members 51 and 59 may be replaced by any other equivalentmember.

It willbe seen thattheadjustment is constant in operation and gives fullautomatic control for uneven wear, a feature which is highly desirablefor brakes ofthe self-wrapping type, which, in some forms,.have a .hightendency to uneven wearJ I claim:

1. In a brake of the type including a brake drum, a, relatively fixedback plate for said drum,

.apairiof arcuate shoes within said drum, brakeoperating means forexpanding one pai of adjacent ends of the shoes against the drum, anexternally threadedfinger connected with each shoe at the other pair ofthe adjacent ends of the shoes, a'support'carried by said back plate,and an internally threaded sleeve receiving said fingers and slidablycarried by said support, the

combination with said sleeve of a resilient member surrounding saidsleeve and having one part fixedly connected with the back plate andanother part of said member frictionally surrounding said sleeve .tonormally follow and recentersaidsleeve but to. slipalongsaid sleeve uponexcessivemovement thereof to efieot a new centering ofsaid sleeve.

2. A brake, as defined in claim, llwhereinsaid resilient membercomprises a spiral spring.

3. A device as defined in, claim 1 wherein said resilient membercomprises a spring washer.

4. A device as defined in claim 1 wherein said member is of annular.form and normally at right angles to said sleeve, said member beinghoused within an internal oblate; spheroidal recess in said support, theside walls of said recess forming stops to limit'the movement of saidmember in following said sleeve.

PIERRE FARKAS.

REFERENCES CITED The, following references are of record in the file ofthis patent:

UNITED S'I. Fl'ITFS PATENTS Number Name Date 2,124,786 La Brie July 26,1938 2,132,049 Schlumbrecht Oct. 4, 1938

